JPS60204877A - Formation of thin film - Google Patents

Abstract

PURPOSE:To form uniformly a dense thin film having high quality over a large area in formation of the thin film in which sputtering is utilized by controlling the flow rate of supply gas, the atomic weight of the gas, the pressure in a vessel, the atomic weight of a target and the space between the target and a substrate by the specific equations. CONSTITUTION:A target 2 and a substrate 3 are disposed to face each other in a vessel 1 having a gas supply line 5 and discharge line 6 and a target 2 is sputtered by the gaseous ions formed by glow discharge of supply gas to form a prescribed thin film on the substrate 3. The flow rate of the supply gas, designated as Q(SCCM), the atomic weight of said gas as MG, the pressure in the vessel 1 as P(Torr), the atomic weight of the target 2 as Mr and the space between the target 2 and the substrate 3 as d(cm) are so controlled as to attain 0.5X10<-3=P<=20X10<-3>, P/Q<=2X10<-3>, 0.001<=Pd, Pd<=(Ma+Mr)<2>/20MaMr.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method of forming a thin film of a metal compound or the like using sputtering.

[Technical background of the invention and its problems]

Till! using sputtering phenomenon! As a technique for forming a target material, the gas ions generated by glow discharge of a rare gas such as Ar, Kr, or Xe are accelerated in a strong electric field region formed near the target, and the target material is released by sputtering using these gas ions. A technique is known in which this is deposited on a substrate facing a target. This sputtering method can form S* of a metal compound on a large-area substrate with a simple equipment configuration, so it is used in a wide range of fields such as corrosion-resistant, decorative, and other functional 11111 coatings. .

However, 111Q formed by sputtering method
The quality of glow discharge depends not only on the target material but also on the parameters of the glow discharge, and even at a practical level, accidents (low quality, lack of reproducibility, etc.) due to inadequate discharge parameters are currently occurring. .

[Purpose of the invention]

In view of the above-mentioned points, the present invention makes it possible to uniformly form a dense, high-density MN film over a large area while minimizing damage caused by the incorporation of impurities by defining glow discharge conditions. The purpose of the present invention is to provide a thin film forming method that makes it possible to form a thin film.

[Summary of the invention]

The present invention firstly provides that the supply gas pressure P [torrl in the sputtering container is 0.5X1o'3 or more, 20X1
0-3 or less. The lower limit is necessary to obtain a thin film with little damage, and the upper limit is a necessary condition to obtain a uniform ill film over a large area. Second, when the supply gas flow rate is Q [SCCM], one shift of P/Q is 2×1
0°3 or less. This is an important condition in order to reduce the incorporation of impurities into the formed thin film to within 1 minute.

Third, the atomic mass of the target is My, and the atoms of the supply gas are
When Ma is the distance between Targetera 1~ and the substrate is d[cII, Pd≦(Ma+Mr)2/20~Ia M
Set the condition to be T. This is important in obtaining a dense thin film. However, if Pd is too small, the discharge will become unstable, so the lower limit is set to 0.001.

Further, when the supplied gas is a multi-component gas, Ma is the sum of the atomic weight of each element x the atomic component ratio, and the same applies to MT when the target is multi-component.

〔Effect of the invention〕

According to the present invention, by optimally designing the glow discharge conditions, it is possible to obtain a dense, high-quality, and uniform fill over a large area with less incorporation of impurities and damage to the thin film obtained by sputtering. can.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram of a parallel plate type sputtering apparatus used in carrying out the present invention. In the figure, 1 is a thin film forming container, 2 is an 8 inch diameter target, 3 is a 120 s diameter substrate, 4 is an RFIIL 5 is a gas supply system, and 6 is an exhaust system.

With the above configuration, after the container 1 is evacuated, the gas supply system is operated to introduce gas into the container 1 at a constant flow rate, and after the gas pressure inside the container 1 is kept constant, the power source 4 is turned on. power is applied to target 2. As a result, a gas glow discharge is excited between the target 2 and the substrate 3, and a high electric field region called a cathode dark region is formed near the target. The gas ions during the glow discharge are accelerated in the direction of the target 2 in this high electric field region, collide with the target 2, and sputter and release the target material, and the released particles are deposited on the substrate 3 placed opposite the target 2. fil
It will be served as l.

Using the above device configuration, Fe and T are used as targets 2.
Experiment to form a thin film by using two types of gases, Ar gas and Xe gas, and changing the pressure P of the gas supply, the flow IQ, and the IIl distance d between the target 2 and the substrate 3. I did this. Hereinafter, the usefulness of the present invention will be clarified with reference to the experimental data.

FIG. 2 shows data obtained by measuring the thickness distribution of the formed thin film. This uses Fe target 1- and Ar gas, gas flow layer Q is 24 [SCCM], and RF power is 3
00 [W], target-substrate distance d is 75 [a
e+], and the gas pressure is 2 [mtorr] and 50 [mtorr].
Samples were formed by performing sputtering for 10 minutes for two types of cases with a radius of 3 m torrl on the substrate.
These are the results of measuring film thickness in the range of [α] to 6[1].

The vertical axis in FIG. 2 is the film deposition rate (the value obtained by dividing the film thickness by the sputtering time), and the horizontal axis is the distance from the center of the substrate. As is clear from the figure, the stacking velocity of the membrane j is gas pressure 50 [m
The film thickness is larger in the case of torrl than in the case of 2 [mtorr], but the film thickness is significantly non-uniform at 50 [mtorr]. FIG. 3 shows data showing the relationship between deposition rate gradient and Ar gas pressure. The vertical axis in FIG. 3 is indicated by the slope of the straight line connecting the plot points in FIG. 2, and the smaller the numerical value in FIG. 3, the better the uniformity of the film thickness.

Depending on the application of the thin film, the uniformity of the film thickness may not be so important; for example, the average film thickness i oo.

A loose specification that allows a film thickness distribution within ±250E on a substrate with a radius of 5 [α] for a [human] film (even in the case of Thailand,
It is clear from FIG. 3 that the gas pressure must be kept below 20 m torr. Why does the film thickness become uneven when the gas pressure is high?

This is because the distribution of gas ion density during glow discharge becomes biased toward the vicinity of the central axis of the discharge as the gas pressure increases.

On the other hand, if the gas pressure is too low, the film deposition rate will decrease as described above. For example, other than gas pressure
Under the same conditions as shown in the figure, when the gas pressure is 0°5 m torr, the deposition rate is 50 [person/min] and 2 [mt
orr]. Furthermore, at lower gas pressures, the energy of gas ions incident on the membrane surface increases excessively, resulting in greater damage to the membrane.

For the reasons stated above, the gas pressure is set at 20 [mt] in order to form a thin film with a uniform thickness on a large area substrate.

rrl or less, and in order to quickly form a film, it should be set to O15 [mtorr] or more.

Next, the relationship between gas pressure P and gas flow IQ will be explained.

The amount of leakage from the container of a normal Nll forming device is 10°' [
m torr・I/5ecl, and this is scc
The unit of M is [118, which is 7.9X10' [SCCM]. A process gas (in the case of the present invention, Ar) is placed in a container having this level of vacuum leakage.

When Q [SCCM] is flowed (Kr, Ke) and the pressure inside the container is maintained at P [torr], the impurity gas partial pressure p c [torr] is (Q)7/9xlO), Pc= The impurity gas particle layer fine [c*4sec'] which is given by 7.9x10p/Q [torr] and incident per second per unit area of the substrate is nc"; 3.54
X10 xpc -2,8x10 P/Q. On the other hand, the density of target particles incident per second per unit area of the substrate nT [c*4s e c']
When the deposition rate of the film is D [seC'l] and the atomic diameter of the target particle is a [man], it is given by rLr'=DX 10 /a3. a43 [person] and D42 [person 5ec
4]! : Then, nr47.4×, o++. In order to obtain a film with few impurities, n7 must be greater than no. Ar as gas, Tb and Fe as targets
A TbFe film was formed using a mixed target (30% Tb) with RF power of 300 [W] and varying P/Q. As a result, P/Q≦2X10' [torr/SC
CM] (nc≧1, l×104n), whereas P/Q≧3×10°′ [t
orr/S CCMI (nc≧1.lX104ny
In the range >, the influence of impurities was large, resulting in an in-plane magnetized film. The allowable amount of impurities contained in the membrane varies depending on the membrane's use, but according to the above experimental results, the process gas pressure P
Tojj Sum Q +7) Ratio P/Q 1. t
It should be set to 2×10°3 [tOrr/SCCM] or less.

FIG. 4 is a diagram showing actually measured data of the atomic number density (corresponding to the denseness of the film) of the film. There are two types of gas: Ar and Xe.
Targetera 1- uses two types of Fe and Tb, and forms samples with RF power of 300 [W], gas of 1124 [SCCM], and target-substrate distance of 75 [jw+].
The mass of the membrane was measured by optical emission spectroscopy using inductively coupled plasma, and the atomic number density was calculated by dividing it by the volume of the membrane. In order to avoid errors due to film thickness gradients, the shape of the sample was a ring concentric with the substrate holder.
In the e-target combination, the gas pressure is 10 mtor
r], the atomic number density of the film is F of the bulk body-centered cubic crystal.
The density of e is 8.5×10 [a-3] GC near illumination, but at 10 [mtorr1 or higher, the density of the film decreases. In the combination of Ar gas and Tb target, in the gas pressure range below 3 Q [mtorr], the atomic number density of the capacitor is 3,1X, which is the density of bulk hexagonal Tb.
It is maintained at a value close to 10. In the combination of Xe gas and Tb target, the denseness of the film decreases at a gas pressure of 10 m torr or more.

Particles that are incident on the substrate surface include sputter gas particles and impurity gas particles in addition to target particles, but among these particles, sputter gas particles have the highest incidence frequency. In order for the film to be dense, it is necessary for the target particles to repel the layer of sputtered gas particles physically adsorbed to the substrate surface or film surface when the target particles are attached to the substrate surface, and to become an am-forming factor. This requires that the target particles have a certain amount of energy. The energy of the target particles when sputtered and emitted from the target surface is on average about 10 [eV], which is sufficiently large, but the sputtered particles collide with gas particles in the gas phase before depositing on the substrate surface. and lose energy. The energy lost from sputtering until it hits the substrate is given by the product of the number of collisions and the energy lost in one collision. The energy coefficient lost in − collisions is
Using the atomic weight MT of the target particle and the atomic layer Ma of the gas particle, it is given by 2MaMy/(MO+MT)2, and the number of collisions is determined by the gas pressure P and the target-substrate distance d.
It is proportional to the product pd. Therefore, in order to obtain a dense film, Pd X 2Ma My / (MG + MT) 2
must be smaller than a certain value, and from the above data, if Pd≦(MO+MT)2/20MG MT, then 1! It can be seen that the density is maintained at about 90% or more of the bulk.

On the other hand, if pd is too small, the discharge starting voltage will increase.

Discharge becomes unstable. Pd
The lower limit of 0.001 [t.

An appropriate value is r'.α].

As described above, by sputtering according to the set conditions of the present invention, it is possible to uniformly form a dense thin film over a large area with little damage or impurity incorporation.

Note that the present invention is based on the si! It is not limited to the formation method,
It can be applied to all 1M forming methods that utilize sputtering phenomena, such as DC sputtering, magnetron sputtering, coaxial sputtering, multi-pole sputtering, and one-reactive sputtering.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a sputtering apparatus for explaining an embodiment of the present invention, FIG. 2 is a diagram showing a formed N-type film deposition rate distribution, and FIG. 3 is a diagram showing the film deposition rate gradient and gas FIG. 4 is a diagram showing the relationship between the atomic number density and the gas pressure of a similarly formed film. 1... NNI formation container, 2... target, 3...
・Substrate, 4...RFI source, 5...Gas supply system, 6.
・Exhaust system. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (1)

[Claims] A target and a substrate facing the target are arranged in a container having a gas supply system and an exhaust system, and the target is sputtered onto the substrate by gas ions generated by glow discharge of the supply gas. Predetermined WIl! , the flow rate of the feed gas is Q [SCCM], the atomic weight of this gas is Ma, and the pressure inside the container is p [tOrr].
, When the atomic weight of the target is M T s and the distance between the target and the substrate is d [cIR], ■0.5X10'≦P≦20X10'3■P/Q≦2X
10-3 (1) An ms forming method characterized by satisfying the following conditions: 0.001≦Pd and Pd≦(Ma~IT)t/20MGMT.